Depends on where your getting in the kayak from and how your boat ladder is configured, but the method we used in whitewater kayaking was to lay your paddle across the kayak, just behind the seat, with one end supported by the bank, your ladder, the dinghy, or whatever else might be solid and handy. when you place your weight on the paddle shaft between the kayak and support, the kayak under it will be quite stable and allow you to get seated. a little practice near shore would be advised, but it's really pretty easy.
edit:
OOps. sorry if I stepped on the guest speaker. I just noticed this is from his column.
Russ